Process for the production of filmlike bands from cellulose solutions and similar initial materials



1,641,322 E. CZAPEK ET AL TION OF FILM LIKE BANDS FROM CELLULOSE Sept.6, 1927.

PROCESS FOR THE PRODUC SOLUTIONS AND SIMILAR INITIAL MATERIALS FiledJan. 15. 1926 Patented Sept. 6, 1927.

UNITED STATES PATENT OFFICE.

EMIL CZAPEK AND RICHARD WEINGAND, OF BOMLITZ, NEAR WALSRODE, GERMANY.

PROCESS FOR THE PRODUCTION OF FILMLIKE BANDS FROM CELLULOSE SOLUTIONSAND SIMILAR INITIAL MATERIALS.

Application filed January 15, 1926, Serial No. 81,557, and in GermanyOctober 15, 1821.

This invention relates to the production of film-like bands fromcellulosic or similar viscose substances, the cellulosio material beingapplied to a conveying band, which band 8 with the cellulosic materialthereon is passed through a precipitating bath, in which the material onthe band is subjected to the precipitating action of an electriccurrent, the electric current acting progressively on the 10 materialapplied to the band during the travel of the hand through the bath.

According to this invention the action of an electriccurrent is employedfor the production of insoluble.film like ribbons from cellulosicsolutions, viscose or gelatine and the like, in a new and advantageousmanner, being applied so that electrolysis and precipitation may takeplace in the alkaline, then in the neutral and finally in the a'cidportions of a bath situated between the electrodes, the film-material asa cellulosio solu tion being first coagulated in a weakly alkalineportion of a salt solution; it then reaches the neutral portion of thebath and is thereafter submitted to the action of the acid portion ofthe bath. The alkaline, neutral and acid portions of the precipitatingbath act upon the film on the carrier in progressive order and under theinfluence of the electric current. the precipitating bath serves as anelectrolyte, exhibiting an alkaline reaction at the cathode or negativepole and an acid reaction at the anode or positive pole while'acontinuous graduation from the alkaline to the acid zone exists duringthe passage of the currentbetween the two electrodes, so thatthe centralportion of the bath becomes neutral. There is no need to .fear anymixing ofthc precipitating bath if a suitable, not too rapid, speed'ofpassage of-the film is maintained.

Inasmuch as according to the invention, the film upon the conveying bandis passed at the requisite speed, i. e.. sutficiently slowly through theregion of action of the electric current a very slow and exceedinglyuniform 'oa ::ulation and a particularly favourable hardcningof thefilmtakes place. A further advantage is that the alkaline and the acidtreatment. of the film are not effected in the usual manner in twoseparate baths but in a.

single precipitatin bath. Aprecipitation on both sides is a soattained"because the bath li uor penetrates the pores of the conveyingand and also because the conveying band is already, on application ofthe cellulose or viscose solution, moistened with the thin layer ofprecipitating agent, the action of which is increased and activated bythe electric current. By'virtue of the em loyment of a eonveying'band,tearing, ro llin up of the film and shrinkages are avoide whichdisadvantages can easily occur durin precipitation on both sides withthe aid 0 small closely adjacent rollers for alternately guiding thefilm.

The present process canbe applied to all cellulosic solutions whichcontaln inor anic electrolytes such as sodium hydrates, su phuric acid,zinc chloride, calcium rhodanite, cuprammonia and the 'like. A fabricim-- prcgnated with celluloid, bakelite or similar substance stable inthe conditions of comparatively low alkalinity and acidity of the bathis preferably employed as conveying hand. The conveying band and thefilm are preferably guided between the electrodes transversely to thedirection of the current in several windings. Since highly viscoussolutions such as viscose and the like'are em- U ployed in theproduction of film-like bands there is no fear of the solution runningoff the conveying band.

The effect of the direct electric current can be simultaneously employedincarrying out the invention, to bring the preci itating bath to therequired temperature. or this purpose the current strength. and thedistance between the electrodes or the concentration of the bath are soselected that the electric current exercises a heatin action whichmaintains the bath at the esired temperature The employment of theaction of the electrical current for the production of films accordingto the invention moreover offers the possibility of simultaneouslyincorporating a dye into the film by means of the current, in order toproduce permanently colloured films. For example there may be added tothe alkaline part of the bath an acid dye which is soluble in this partof the precipitating bath and which has a tendency to move towards theanode. In doing so, it must pass through the film and is taken up by thelatter reaching the acid part of the bath together with the film and isrendered insoluble.

All acid dyes such as for instance alkaliblue, green, dianil black maybe employed for the aforesaid purpose.

In order more clearly to understand the invention reference is made tothe accompanyingdrawings, Fig. 1 of which illustrates diagrammaticallyone embodiment of apparatus suitable for carrying same into practicalefiect.

Fig. 2 is a detail longitudinal section taken ilon itudinally throughtwo of the upper gui e rollers and through a single lower roller, andFig. 3 is a detail view partly in section of the lower guide roller,with film carrying belt thereon.

In said fi ures, -1 indicates the container containing t e usualprecipitation bath containing sodium sulphate. Two electrodes 2 and 3 ofmetal, graphite, carbon or the like are arran ed within said container 1and are connecte to a source of direct current. The conveying band 4upon a part thereof which is beyond the container will have applied toits upper surface, by any suitable means, as a pourer, a cellulosic orviscose solution, the band with the coating 4 thereon being carriedthrough the bath by means of rollers 5 in several loops to form a longpath for the applied film. In consequence of the difference in potentialthe precipitation bath exhibits an alkaline reaction at the inlet end,thus consisting at this point of a solvent mixture of sodium sulphateand sodium hydroxide. The conveying band with the partly coagulatedviscose thereon passes into the central part of the precipitation bathwhich is composed of neutral sodium sulphate solution. Up to this pointthe coagulated viscose mass is still soluble in water. 'However in thesubsequent portion of the bath which consists of a solvent mixture ofsodiu sulphate and sulphuric acid it becomes insoluble in water. At theend of the bath the viscose is completely precipitated throughout and isinsoluble in water so that it can be removed from the conveying band andpassed through the subsequent cold and hot washing baths.

A speed regulator can be arranged in the drive of the conveying band soas to permit the speed of the conveying band to be decreased if desired,in order to utilize all the bath and the electric current actioncorrectly. If it is intended simultaneously to heat the bath by means ofthe electric current, the voltage applied to the electrodes 2 and 3 mustbe correspondingly increased or the distance between the electrodes oralso the concentration of the bath must be altered until therecipitating bath reaches and is maintaine at the desired temperature.

In order to prevent the film pressing on the lower guide roller where itlies between the roller and conveying band, it may be conducted here ina recess in the rollers whilst the conveying band is maintained on therollers and at a certain distance of the film by lateral flanges. Thismethod of guiding the conveying band is illustrated in Figs. 2 and 3,where the lower guide roller 5 is provided with end flanges 6 and 7 uponwhich the conveying band is placed whilst the film 4 is situated in therecess in the roller between these flanges. The film 4' is thus free ofthe pressure of the conveying band 4 which is taken up by the flanges 6and 7 of the roller 5. This expedient thus also prevents excessivestressing of the film when lying on the inside beneath the guiderollers.

Having now particularly described and ascertained the nature of our saidinvention and in what manner the same is to be performed, we declarethat what we claim is 1. The method of making film-like bands fromcellulosic material which contains inorganic electrolytes, whichconsists in passing a carrier having a film of cel'lulosic materialthereon, in passing such carrier into and out of a precipitating bath,directing a current of electricity through the bath, and actuating thecarrier at such a speed that the alkaline, neutral and acid zones of thebath act upon the film on the carrier progressively. V

2. The process of producing film-like bands from cellulosic solutionswhich contain inorganic electrolytes capable of yielding acid, neutraland alkaline zones when subjected to electrolysis, which consists inpassing an electric current through aprecipitating bath heated therebyand guiding a conveying band carrying a film between electrodes andthrough the bath in such a manner that different zones of the bath willact upon the film progressively.

3. In the process of producing a band from ce'llulosic viscose solutionscontaining inorganic electrolytes, which consists in passing through aprecipitating bath a carrier having thereon a film of said viscose, thecarrier and film being caused to travel between electrodes, theprecipitating strength of the bath increasing in the direction of thetravel of the carrier.

4. Means for producing film-like bands of viscose solutions comprising asingle tank for a precipitating bath, electrodes located at oppositeends of the tank which contains the precipitating bath, a travellingcarrier to only one side of which a film of viscose solution is applied,guides for the travelling carrier which maintain the major portionthereof in vertical and parallel alinement with the electrodes toprovide means whereby the film will be progressively acted upon duringits travel throu h difl'erent zones of the bath, the zones havingdifierent degrees of precipitating powers.

5. The method of making film-like bands from cellulosic solutions whichcontain inorganic electrolytes, which consists in passing an electriccurrent through a precipitatin bath, passing a carrier having a film ofcellulosic material on one of its surfaces bet-ween electrodes in saidbath, moving said carrier at such speed that-the alkaline, neutral andacid portions of the bath act upon the film progressively, said film ofcellulosic material also being affected by porated with the bath.

6. A step in the process of forming filmlike bands from a viscosesolution which consists in subjecting a film applied to a carrier totravel into and through a precipitating bath, the carrier being guidedso that the carrier and film thereon will travel substantially parallelto an anode and cathode located at opposite ends of the bath.

In testimony whereof we aflix our signatures.

a dye incor- DR. EMIL CZAPEK. RICHARD WEINGAND.

